Up to now, in transmitting video signals to a liquid crystal display or a CRT, the mainstream has been to use an analog RGB interface to send video signals by analog transmission. However, in e.g., a liquid crystal monitor, the number of pixels that can be demonstrated is predetermined, such that, as the liquid crystal monitor has come into popular use, digital transmission has attracted attention. On the other hand, there is felt a need to increase the refresh rate for decreasing flicker, while there is also felt a need to send data at a high rate for displaying a picture on a screen of wider format. In the conventional analog transmission, transmission distortion is significant, such that ghost tends to be produced. Under this situation, more and more importance is attached to digital transmission in keeping up with the tendency towards higher picture quality.
For meeting the demand for digital transmission, DVI (Digital Visual Interface) has stirred up notice. This DVI is an interface for digital display connection defined by DDWG (Digital Display Working group) and transmits data using plural data channels based on the TMDS (Transmission Minimized Differential Signaling)technique. With use of the digital transmission method, employing DVI, it is possible to provide high quality video data of low transmission distortion at a low cost.
By employing the DVI, pictures of higher picture quality than are possible with analog transmission can be achieved. Moreover, the DVI provides, in addition to a period during which pixel data of RGB (red, green and blue) is transmitted, a blanking period during which it is possible to transmit data other than the RGB pixel data. This blanking period may be utilized to transmit audio signals, as an example.
In transmitting digital video signals, there may be produced transmission errors, such as garbled bits. In the case of video signals, transmission errors, if produced, are not outstanding on a screen, such that no serious problems are raised. However, if transmission errors are produced during transmission of audio signals, noises or extraneous sounds may be produced, and hence the problem of error rate needs to be tackled more rigorously than in the case of transmitting video signals. Specifically, if data other than video signals, that is data in which errors appear as outstanding, is to be transmitted during the blanking period of DVI, separate processing for error detection and correction is needed. Since in general the processing for error detection and error correction necessitates a larger quantity of hardware, the size of the apparatus tends to be increased, thus raising the cost.